The invention described below relates to the field of automatic control of fluid flow, and it finds particular application in watering devices of the type used in lawn watering, gardening, and irrigation.
In the course of watering lawns and home gardens, the problem is often encountered that the soil is such that it cannot absorb enough water to properly support the desired plant life. That is, sandy soils retain very little water, allowing most of it to flow through, while clay soils cause much of the water to run off. The solution to this problem is to water in a very slow manner, thereby supplying only the amount of water that can be retained or absorbed by the soil.
In order to supply the water in this manner without constant human attention, devices have been employed in the past that automatically turn the water supply on and off, thereby providing water on a long-term basis but avoiding overwatering.
When such devices are intended for the home market, it is important that they be simple, inexpensive, and unlikely to cause damage to the lawn or garden with which they are used. An example of an attempt to fulfill these requirements is described in Jones, U.S. Pat. No. 3,865,138, in which a solenoid-actuated value is controlled by a timer. That arrangement is relatively simple, but certain improvements may be desired. For instance, the use of an ordinary timer of the type normally available to the consumer is geared to the twenty-four-hour day so that water can be turned off and on a very limited number of times in an entire day. If such a device is timed to stay on for the approximate amount of time required to supply as much water as the ground can take, it will typically be on for a very short time, will then be turned off, and for the rest of the day will permit the ground to dry out. What would be more desirable would be a provision of a large number of relatively short on times throughout a day. However, such an arrangement would not be feasible with the type of inexpensive timer normally available. In addition, the provision of a timer, even a relatively inexpensive one, does add significantly to the cost of what should be a low-priced item. Finally, if the timer used with the Jones arrangement should malfunction and permit continuous operation of the watering throughout the day, a good deal of irreversible damage could conceivably be done to the garden.